=========================== Introduction to PyFiberAmp ===========================

PyFiberAmp is a rate equation simulation library for rare-earth-doped fiber amplifiers and fiber lasers partly based on the Giles model [1]_.

NEW in version 0.5.0:

• Integrated LP mode solver + support for user-defined mode shapes
• Improved plotting functions
• Ability to use fully 2D doping/inversion profiles in the core
• Different background loss for each channel
• Steady state model now supports reflections
• Python 3.9 support for C++ addon
• License change to GPL3

With PyFiberAmp you can simulate:

• Both core-pumped and double-clad fiber amplifiers
• Simple continuous-wave, gain-switched and Q-switched fiber lasers
• Unlimited number of pump, signal and ASE channels
• Limited number of Raman channels
• Arbitrarily time-dependent beams from continuous-wave to nanosecond pulses
• Radially and rotationally varying dopant concentration and inversion
• Any LP mode shapes, including dispersion and effective area estimation using the built-in mode solver
• Also Gaussian, top-hat and user-defined mode shapes

Additional benefits include:

• Built-in plotting commands: easy visualization of results
• Python interface: convenient for post-processing the data
• C++, Numba and Pythran backends: fast time-dynamic simulations
• Open source: see what's happening under the hood
• Free of charge: install on as many computers as you like

Documentation is still in progress and available at pyfiberamp.com <https://pyfiberamp.com>_. For practical examples, see the examples folder above. If you have a question, comment or feature request, please open a new issue on GitHub or contact me at pyfiberamp@gmail.com. If you find PyFiberAmp useful in your own project, I would also very much like to hear about it.

If you want to simulate nonlinear and/or dispersive pulse propagation in fiber amplifiers, the new pyLaserPulse <https://github.com/jsfeehan/pyLaserPulse>_ package looks like a promising option, though I have not tested it yet myself.

A visual example ================= Few-nanosecond pulses propagating in an Yb-doped fiber amplifier are distorted because of gain saturation. The Gaussian pulse with its exponential leading edge retains its shape better than the square or saw-tooth pulses.

.. image:: docs/images/pulses.gif :align: center

Download ========= PyFiberAmp is not yet on PyPI. You can either download the code as a zip-file or clone the repository with ::

git clone git://github.com/Jomiri/pyfiberamp.git

and then install the library by executing ::

python setup.py install

in the (unzipped) download directory.

System requirements =================== PyFiberAmp depends on the standard scientific Python packages: Numpy, SciPy and Matplotlib and has been tested on Windows 7 and Windows 10. It should work on other operating systems as well provided that Python and the required packages are installed. The Anaconda distribution <https://www.anaconda.com/download/>_ contains everything you'll need out of the box.

Even though all of PyFiberAmp's functionality is available in interpreted Python code, the use of one of the compiled backends (C++, Numba or Pythran) is recommended for computationally intensive time-dynamic simulations. The hand-written C++ extension is fastest but has also the strictest system requirements: Windows 7 or 10, Python 3.9 and a fairly modern CPU with AVX2 instruction support. The Pythran backend probably only works on Linux and requires that pythran <https://pythran.readthedocs.io/en/latest/>_ is installed before installing PyFiberAmp. The Numba backend should work on all operating systems provided that Numba <https://numba.pydata.org/>_ is available. Please open a new issue if you encounter problems with a backend that should work but does not.

Note that the C++ extension has been bumped to support Python 3.9 in version 0.5.0.

Example ======== The simple example below demonstrates a core-pumped Yb-doped fiber amplifier. All units are in SI. ::

from pyfiberamp.steady_state import SteadyStateSimulation from pyfiberamp.fibers import YbDopedFiber

ybnumberdensity = 2e25 # m^-3 core_radius = 3e-6 # m length = 2.5 # m core_na = 0.12

fiber = YbDopedFiber(length=length, coreradius=coreradius, ionnumberdensity=ybnumberdensity, background_loss=0, corena=corena) simulation = SteadyStateSimulation(fiber=fiber)

simulation.addforwardsignal(wl=1035e-9, input_power=2e-3) simulation.addforwardpump(wl=976e-9, input_power=300e-3) simulation.addase(wlstart=1000e-9, wlend=1080e-9, nbins=80)

result = simulation.run(tol=1e-5) result.plot()

The script calculates and plots the power evolution in the amplifier and the amplified spontaneous emission (ASE) spectra. The co-propagating pump is absorbed in the first ~1.2 m of the fiber while the signal experiences gain. When the pump has been depleted, the signal starts to be reabsorbed. ASE is stronger against the pumping direction.

.. image:: docs/images/readmepowerevolution.png :align: center

.. image:: docs/images/readmeasespectra.png :align: center

For more usage examples, please see the Jupyter notebooks in the examples folder. More examples will be added in the future.

Fiber data ========== PyFiberAmp comes with spectroscopic data (effective absorption and emission cross sections) for Yb-doped germanosilicate fibers [3]_ and supports importing spectra for other dopants and glass compositions.

Theory basics ============== For a quick review on the theory, see the pyfiberamp theory.pdf <https://github.com/Jomiri/pyfiberamp/blob/master/pyfiberamp%20theory.pdf>_ file. Theory on the time-dynamic simulations is not yet included. A more complete description can be found in the references.

License ======== As of version 0.5.0 PyFiberAmp is licensed under the GPL3 license. The C++ extension depends on the pybind11 <https://github.com/pybind/pybind11> and Armadillo <http://arma.sourceforge.net/> projects. See the license file for their respective licenses.

References =========== .. [1] C.R. Giles and E. Desurvire, "Modeling erbium-doped fiber amplifiers," in Journal of Lightwave Technology, vol. 9, no. 2, pp. 271-283, Feb 1991. doi: 10.1109/50.65886 .. [2] R.G. Smith, "Optical Power Handling Capacity of Low Loss Optical Fibers as Determined by Stimulated Raman and Brillouin Scattering," Appl. Opt. 11, 2489-2494 (1972) .. [3] R. Paschotta, J. Nilsson, A. C. Tropper and D. C. Hanna, "Ytterbium-doped fiber amplifiers," in IEEE Journal of Quantum Electronics, vol. 33, no. 7, pp. 1049-1056, Jul 1997. doi: 10.1109/3.594865